A portable gasoline tool is often used in the area of garden greening, and its electronic ignition system is a key system therein. The electronic ignition system mainly comprises a flywheel, a voltage boosting device, and a spark plug, and mainly functioning to ignite, with a spark produced by the spark plug driven by a high voltage coil, the combustible gas mixture introduced into the combustion chamber, to make it explode to release energy. In addition, the electronic ignition system operates at a most suitable ignition angle and gives out sufficient ignition voltage such that the gasoline engine of the portable gasoline tool can run smoothly and has an improved efficiency. Currently, the commonly used electronic ignition system comprises a magnet motor, an igniter, an inductive coil provided on the cylinder, and a permanent magnet mounted on the flywheel. The permanent magnet is rotated with the flywheel, and every time it meets the inductive coil fixed on the cylinder around a circle, an inductive current is produced in the inductive coil (as in an electric generator in principle). The higher the rotation speed of the flywheel is, the larger the inductive current produced; the lower the rotation speed, the smaller the inductive current. An electric circuit is used to amplify the coil inductive current into a voltage of tens of kV such that the spark plug connected thereto and placed in parallel in the combustion chamber of the gasoline engine, ignites. However, the electronic ignition system has the following defects: the voltage is proportional to the rotation speed, and when the rotation speed is relatively low, the produced inductive current is small and the ignition voltage is relatively low, wherein the relation of the ignition time point, the ignition voltage, and the rotation speed is shown in FIG. 1. Moreover, in the start-up stage, the rotation speed is relatively low, the ignition voltage cannot produce a large spark needed at this time and it is adverse to ignition, resulting in the difficulties to start the gasoline engine for the user to employ.